In this paper, we present an automated bus matrix synthesis flow for efficient system-on-chip communication design space exploration at the transaction level. Especially, we consider hardware interface design, since it affects overall system cost and performance. Depending on the bus interface, a hardware block can be a master or a slave. We propose a method to solve such hardware interface selection problem by analyzing communication behavior statically. In addition, in order to explore communication design space fast, we automatically generate transaction level models for the hardware blocks according to the hardware interface selection. The synthesis result is verified by transaction level simulation with a commercial tool. We give experimental results with JPEG encoder and H.264 encoder to demonstrate the efficiency of the proposed method. The results show that with our automated synthesis flow, the designer can easily and quickly obtain better communication designs through fast design space exploration. More specifically, our hardware interface selection technique is successful in achieving reduction of area of bus matrix by 41.43% with 0.58% performance overhead on average compared to the case of maximum performance.